Identifying Look-alike Parthian Bronzes

In An Introduction to the Coinage of Parthia (1980), Sellwood gives descriptions without illustrations of the bronzes of Osroes II (types 85.4 & 84.5) and Artabanus IV (type 89.6). The descriptions are virtually identical. Here is how to differentiate the two types:

It is very difficult to be absolutely sure identifying these types, especially when the obverse portrait is either off-center or not fully struck up on a small flan and thus the tip of the beard is off-flan, hiding whether it is forked (Artabanus IV) or not (Osroes II). But the Artabanus examples always display a much finer portrait than those of Osroes, although still crude. It is exactly like comparing the drachms of the two kings; Artabanus looks better. Another deciding factor is that on an Artabanus chalkous, you tend to see the obverse letters even if the coin is in a poor state.